//函数表达式
var func = function(a,b){
	return a + b;
};
console.log(func(5,20));

//立即调用函数，避免全局污染，即括号里面的变量不会影响到外面所设的同变量名的值
(function() {
	var a = 5;
	var b = 3;
	var c = a + b;
	console.log("c=" + c);
})();//最后加括号表明调用该函数

!function() {
	var a = 20;
	var b = 30;
	console.log(a + b);
}();

(function(a , b){
	console.log(a + b);
})(5,20);